Does Blender keep a log when it's rendering?
Here's a quick script you can use to output some simple frame times:

import bpy
from bpy.app import handlers
from datetime import datetime


def render_init_handler(dummy):

    global LASTFRAME
    global STARTTIME

    STARTTIME = datetime.now()
    LASTFRAME = datetime.now()


def render_post_handler(dummy):

    global LASTFRAME
    global STARTTIME

    ELAPSEDTIME = datetime.now() - STARTTIME
    FRAMELENGTH = datetime.now() - LASTFRAME
    frameNum = bpy.context.scene.frame_current
    blendName = bpy.path.basename(bpy.context.blend_data.filepath)[:-6]

    f = open(bpy.path.abspath("//") + blendName + '-renderlog.txt','a')
    f.write("Frame %d - Length: %s - Elapsed: %s\n" % (frameNum,FRAMELENGTH, ELAPSEDTIME)) 
    f.close()

    LASTFRAME = datetime.now()

handlers.render_init.append(render_init_handler)    
handlers.render_post.append(render_post_handler)


You should generate a text file that looks like this inside:

Frame 1 - Length: 0:00:00.139432 - Elapsed: 0:00:00.139441
Frame 2 - Length: 0:00:00.232712 - Elapsed: 0:00:00.372586
Frame 3 - Length: 0:00:00.257580 - Elapsed: 0:00:00.630437
Frame 4 - Length: 0:00:00.265303 - Elapsed: 0:00:00.895999
Frame 5 - Length: 0:00:00.259570 - Elapsed: 0:00:01.155840
Frame 6 - Length: 0:00:00.266500 - Elapsed: 0:00:01.422597
Frame 7 - Length: 0:00:00.260504 - Elapsed: 0:00:01.683389
Frame 8 - Length: 0:00:00.259319 - Elapsed: 0:00:01.942971
Frame 9 - Length: 0:00:00.258627 - Elapsed: 0:00:02.201868
Frame 10 - Length: 0:00:00.260319 - Elapsed: 0:00:02.462535
Frame 11 - Length: 0:00:00.257915 - Elapsed: 0:00:02.720720
Frame 12 - Length: 0:00:00.261301 - Elapsed: 0:00:02.982309
Frame 13 - Length: 0:00:00.262327 - Elapsed: 0:00:03.244906